1. Field of the Invention
The present invention relates to valve actuating apparatus operable to actuate a downhole valve assembly. In particular, the present invention relates to a valve actuating apparatus that provides a contingency/back-up device operable to actuate a downhole valve that has failed to operate.
2. Description of the Related Art
Well completion involves various downhole procedures prior to allowing production fluids to flow thereby bringing the well on line. One of the downhole procedures routinely carried out during well completion is pressure testing where one downhole section of the well is isolated from another downhole section of the well by a closed valve mechanism such that the integrity of the wellbore casing/liner can be tested.
Well completion generally involves the assembly of downhole tubulars and equipment that is required to enable safe and efficient production from a well. In the following, well completion is described as being carried out in stages/sections. The integrity of each section may be tested before introducing the next section. The terms lower completion, intermediate completion and upper completion are used to describe separate completion stages that are fluidly coupled or in fluid communication with the next completion stage to allow production fluid to flow.
Lower completion refers to the portion of the well that is across the production or injection zone and which comprises perforations in the case of a cemented casing such that production flow can enter the inside of the production tubing such that production fluid can flow towards the surface.
Intermediate completion refers to the completion stage that is fluidly coupled to the lower completion and upper completion refers to the section of the well that extends from the intermediate completion to carry production fluid to the surface.
During testing of the intermediate completion stage the lower completion is isolated from the intermediate completion by a closed valve located in the intermediate completion. When the integrity of the tubing forming the intermediate completion section is confirmed the upper completion stage can be run-in.
Generally the completion stages are run-in with valves open and then the valves are subsequently closed such that the completion stages can be isolated from each other and the integrity of the production tubing and the well casing/wall can be tested.
Typically, the valves remain downhole and are opened to allow production fluids to flow. By opening the valves the flow of production fluids is not impeded.
In the event that a valve fails to open, for example where the valve or an actuating mechanism operable to open the valve becomes jammed, remedial action is generally required because a failed valve effectively blocks the production path.
Remedial action often involves removing the valve. The valve may be removed by milling or drilling the valve out of the wellbore to provide a free flowing path for production fluid.
It will be appreciated that resorting to such remedial action can result in costly downtime because production from the well is stopped or delayed. The remedial action may result in damage to the well itself where milling or drilling the valve or valves from the wellbore may create perforations in the production tubing or the well casing or well lining. As a result such actions would preferably be avoided.
In the above the importance of opening a valve to allow production to flow has been discussed. However, in the situation of a producing well requiring workover it is equally important to be able to isolate sections of the well to stop/halt production flow.
Workover requires that the well is shut-in below the surface or the well must first be killed.
Often in preparation for workover the completion assembly is removed, however, sometimes due to the placement of a packer in the well, for example a permanent packer, it can be problematic to remove a completion string for workover. Therefore, an alternative to retrieving the completion string is to isolate the well by shutting off production by closing a downhole valve. Conventionally, control lines from surface facilitate fluid communication downhole to the valves in order to close the valves.
However, in the event that the valve fails to close other operations to prepare the well for workover may be implemented such as killing the well. A well can be killed by using reverse circulation or by pumping heavy weight fluids into the well. It is desirable to provide a downhole device such that production downtime due to a failed valve is reduced.
It is further desirable to provide an actuating apparatus that provides a secondary actuating mechanism operable to actuate a failed valve located in the wellbore.